4TH LIVER TRANSPLANT FOR 7-MONTH-OLD GIRL

Seven-month-old Meghann LaRocco of the Southwest Side underwent her fourth liver transplant within about a month late Tuesday in a desperate attempt to save her life.

The operation, performed by doctors at the University of Chicago`s Bernard Mitchell Hospital and Wyler Children`s Hospital, began at 6:45 p.m.

''We expect the operation to last anywhere from 6 to 26 hours, but we think it will be something short of 12 hours,'' said Bill Bulger, a hospital spokesman.

Earlier Tuesday, doctors had said Meghann`s chances of survival were only ''50-50,'' providing that they found a healthy, matching liver to transplant to the girl.

Meghann has suffered life-threatening breathing problems since Dec. 20, when doctors implanted a third liver that was too large and had strained the girl`s abdomen, doctors said. A ventilator required to help the infant breathe also threatened to ruin her lungs, said Peter Whitington, the pediatrician supervising Meghann`s care.

Shortly before 4 p.m. Tuesday, doctors and Meghann`s parents learned that a liver apparently suitable for Meghann had been donated from a 10-month-old who had died in the Chicago area.

''This has been a roller coaster,'' said Frank LaRocco, emotionally drained 31 days after his daughter first underwent surgery to replace her natural liver, severely scarred by a genetic disease.

''For seven nights we`ve been sleeping on the floor here at the hospital. But it has felt good to know that a lot of people are rooting for Meghann.''

As Meghann`s parents prepared for a sleepless night, a Dolton couple continued their wait for a liver for their six-week-old daughter, who also is the victim of a genetic disease that is slowly destroying her liver.

The girl, Cora Ann Bogle, must receive a liver within two weeks or she will die, her doctor at Christ Hospital in Oak Lawn said Tuesday.

''We try not to look at the realistic side of it,'' said Allen Bogle, the girl`s father, referring to the chances of receiving a liver within the next two weeks. ''We`re looking for a miracle.''

Like the LaRoccos, Bogle and his wife, Teri, have spent hundreds of hours at the hospital watching their daughter and waiting for word through the national organ transplant computer that a healthy, matching liver is available.

The Bogle girl, born Nov. 14, had been home for less than a week when she became jaundiced and cold. Doctors discovered that she suffered from a liver disease that, while transmitted genetically, is different from the LaRocco girl`s disease.

Teri Bogle now keeps a suitcase at Christ Hospital in case she is with her daughter when word comes that a liver has been found. She and her daughter would fly to Pittsburgh, where they have decided that doctors at Children`s Hospital there will perform the transplant.

The operation is expected to cost about $200,000, Allen Bogle said. Already, he said, his daughter`s medical bills total more than $85,000.

As the two infants clung to life Tuesday, doctors debated the medical ethics of the multiple operations that have kept Meghann alive. The girl`s doctors at the University of Chicago said the second and third livers they had implanted earlier had not prevented Cora Ann or any other child on the national waiting list for liver transplants from receiving the vital organ.

The decisions to transplant the second and third livers were

''questionable,'' said Whitington, the pediatrician. The second liver was too small and the third too large, he said. Also, he said, the third liver was from a youth who had died after being burned. The liver had been damaged slightly because of the burns, he said.

The two organs had been offered first to other transplant patients across the country and been rejected by those patients` doctors, Whitington said. Despite the organs` imperfections, he said, doctors implanted them in the LaRocco child because they were needed to save her life after her body rejected the first transplant liver.

''Sometimes when you`re in a tight spot, you use organs that you might not normally use,'' Whitington said.

''If we hadn`t tried, Megahnn wouldn`t be alive right now,'' said Christoph Broelsch, the surgeon who has performed all of Meghann`s operations and operated on her late Tuesday.

Whitington said he and other doctors treating Meghann never questioned the ethics of obtaining the second, third and fourth livers for the girl. Six other children across the country are listed as ''highest priority'' for livers on the organ donation computer`s national list, Broelsch said. Before Meghann`s second and third liver transplants, doctors for the children on that list, who could have received the liver in time, were offered the organs and declined.

The doctors said they did not know whether the Bogle child was among the six. Cora Ann`s name was added to the computer list Dec. 22, Teri Bogle said. The Bogles said they envied the luck of the LaRoccos and their doctors in obtaining four livers. But they said they felt no ill will toward them. The Bogles said that organs Meghann received were too large to save Cora Ann`s life anyway.

''If you`re an outsider, I can see how it doesn`t seem fair,'' Teri Bogle said. ''But their daughter means everything to them, just as ours means everything to us.''

Olga Jonasson, a professor of surgery at the University of Illinois at Chicago who was chairman of a national panel that recently recommended changes in transplant policy to Congress and President Reagan, said it is easy for outsiders to criticize the University of Chicago doctors.

''When you`re standing there at bedside and dealing with the family it`s another matter,'' said Jonasson, also a surgeon at Cook County Hospital.''You as a physician have made a commitment to do everything possible for the patient. If you don`t, you`re abandoning that patient.''